Many underwater operations, such as drilling for and production of oil and gas, installation and maintenance of offshore structures, or laying and maintaining underwater pipelines require the use of a remotely operated vehicle (ROV).
An (ROV) is a tethered underwater mobile device. ROVs are typically unoccupied, highly maneuverable, and operated by a dedicated crew aboard a vessel. The deployment of an ROV is typically achieved by launching the unit from either a bottom founded host platform, a floating host platform, or from a dynamically positioned marine vessel dedicated specifically for the purpose of supporting an ROV and/or other installation and subsea intervention equipment, e.g. a multi service vessel (MSV).
Often when working in rough seas or in deeper water, a load-carrying umbilical cable is used along with a tether management system (TMS). The TMS can be a large garage-like housing which contains the ROV during lowering. The TMS can also be a separate system which sits atop the ROV.
The purpose of the TMS is to house the tether and ROV during lowering, and lengthen and shorten the tether during operation. The TMS effectively allows power to be supplied to the ROV, as well as minimizes the effect of cable drag where there are strong underwater currents.
The umbilical cable is an armored cable that contains a group of electrical conductors and fiber optics that carry electric power, video, and data signals between the operator and the TMS. Where used, the TMS then relays the signals and power for the ROV down the tether cable.
Both bottom founded and floating host platforms can be fixed in position at the site and are normally engaged in collateral activities such as drilling and offshore production or construction. Thus, the operations of the ROV can be limited according to the distance that the ROV can travel from the host platform as well as by restrictions in operating periods due to the collateral activities of the host platform.
In the case of dedicated vessel deployment such as an MSV, significant costs can be associated with operation of a fully founded marine vessel and its mobilization to and from the ROV work site. Typically, a dedicated MSV may have a crew of twenty, large cranes with Active Heave Compensation (AHC), and other considerable costs not directly related to the operation of the ROV.
ROV operation and monitoring can be controlled from the host platform or MSV by means of an umbilical line between the host platform or MSV and the Tether Management System (TMS) which stores a limited amount of tether to connect to the ROV. It can be seen from this that the operational distance of the ROV can be directly related to the length of the tether capacity on the TMS unit.
A need exists for an improved launch and recovery system that utilizes pass through tether management system concepts and advantages while addressing most prominent drawbacks of current systems.
A further need exists for an improved launch and recovery system that can be containerization for standard shipping that can include simple accurate active heave compensation and that has passive guidance for heavy weather deployments.
A further need exists for an improved launch and recovery system that include redundant passive overload protection that eliminates the need for hydraulic power units and can have easy dead ROV recovery capability.
A further need exists for a pass through tether management system with a tether management component connected to the launch and recovery system enabling a remotely operated vehicle (ROV) to be lifted and deployed in water without the need for an armored umbilical.
The present invention meets these needs.
Embodiments of the present invention are detailed below with reference to the listed Figures.